Usb Transceiver - Renesas M16C Series User Manual

M30240 Group

1.5.4 USB Transceiver

When using the on-chip voltage converter to supply the necessary 3.3V to the driver circuit, a capacitor
network must be connected between Ext. Cap (pin 6) and V
as shown in Figure 1.21. The high frequency 0.1 µF capacitor should be an X7R type or better. The
low frequency decoupling capacitor of 2.2 µF should be of tantalum di-electric or better. The start-up
time for this value of the capacitor is 3.2 ms, approximately (1ms/ µF) + 1 ms.
After enabling the on-chip voltage converter, a certain amount of time must pass before a wait or stop
clock instruction is executed. The amount of time is given by (C+1) ms, when C is the value in µF of
the external capacitance connected to the Ext. Cap pin. For example, if the external capacitance is 2.2
µF, at least 3.2 ms must elapse from the time that the on-chip voltage converter is enabled until a WAIT
instruction or STOP command (CM10 = 1) is executed.
In order to meet the impedance matching requirements of the USB Specification, a 27
must be added to USB D+ (pin 9) and to USB D- (pin 10). In addition, capacitors connected between
USB D+ and USB D- or USB D+/D- and Vss may need to be added for rise/fall time matching and
edge control. These capacitors should be placed after the 33
ues will depend on the PCs layout. The placement of external components is illustrated in Figure .
USB Block
Note: Capacitor and resistor values and configuration may depend on PCB layout.
Figure 1.121: Configuration of External USB components
Rev.1.00 Sep 24, 2003 Page 136 of 360
USB_Vp_out
USB_Txen_n
USB_Vm_out
USB_Suspend
USB_Rxd
USB_Vp_in
USB_Vm_in
(pin 13). Two capacitors are required
SS
Ω
resistors. Their configuration and val-
Voltage Converter
XCV_Vp_out
XCV_Txen_n
XCV_Vm_out
XCV_Suspend
XCV_Rxd
+
_
XCV_Vp_in
XCV_Vm_in
Transceiver
USB Transceiver
Ω Ω
-33 resistor
EXTCAP
2.2 µF 0.1 µF 10%
10%
27-33 Ω
D+
22 pF
33 pF
27-33 Ω
D-
22 pF (Note)